Sicilian smoker (4)
I believe the answer is:
'sicilian smoker' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for etna that I've seen before include "Threatening mountain" , "Sicily's 15" , "Highest peak in Italy south of the Alps" , "Neat class of volcano in Sicily" , "Volcanic mount in Sicily" .)